The present invention relates to improvements in the plating of a gold alloy on metallic surfaces and more particularly to a gold alloy electroplating bath having improved tolerance to metal impurities.
In my co-pending U.S. application Ser. No. 06/270,844, incorporated herein by reference, there is disclosed and claimed a gold alloy electroplating bath and a method for the deposition of a gold alloy layer on a metallic surface from such bath.
The gold alloy electroplating bath comprises an aqueous solution containing a salt of an alloying metal selected from the group consisting of nickel, cobalt and mixtures thereof, the reaction product of an alkali metal-gold cyanide and a mixture of glycolic acid and at least one alkali metal salt of glycolic acid, preferably sodium or potassium. The pH of the bath is maintained at from about 4 to about 5, and preferably from about 4 to about 4.5 by adjusting the ratio of glycolic acid and the alkali metal salt of glycolic acid.
The incorporation of the mixture of glycolic acid and an alkali metal salt of glycolic acid in the gold alloy bath markedly increased the plating rate of the bath.